In the manufacture of microelectronics products and integrated circuits bonding is a mechanical process that also produces an electrical interconnection between two components (for example between an integrated circuit component and the printed circuit board) by means of a metallic bonding wire (for example aluminium, gold or copper). The bonding process generally involves two stages. In the first stage an ultrasonic bonding apparatus touches down on the contact pad and pre-deforms the bonding wire. Then, in a second sage, a burst of ultrasonic energy is applied by the bonding apparatus. In this second stage the bonding apparatus is vibrated and begins with the tool to move together with the wire and removes an unbondable oxide layer (if any) on the surface. Then the wire is caused to deform after an absorption of ultrasonic energy and pressure and a metallurgical bond is formed at the wire-pad interface.
In both these stages there are parameters tat must be monitored. In the first stage the force of impact and the subsequent force applied to the wire needs to measured and monitored for bond quality assurance purposes. In the second stage, the amplitude of the ultrasonic burst and its duration (known as bonding time) both have a significant effect on bond quality and must therefore also be monitored. An optimized range of these bonding parameters which can guarantee the required quality is usually determined for each different type of bonding machine. To ensure that the parameters remain within this range, however, they must be constantly monitored.